The possibility of determining the positions of mobile devices has enabled application developers and wireless network operators to provide location based, and location aware, services. Examples services include guidance/navigation services, shopping assistance, friend finder, presence services, community and communication services, and other information services that give mobile users information about their surroundings.
In addition to commercial services, various governments have imposed requirements on network operators to be able to determine the position of mobile devices engaged in emergency calls. For instance, the so called E911 requirements in the United States mandate that it must be possible to determine the position of a certain percentage of all emergency calls placed from wireless devices. These requirements do not distinguish between indoor and outdoor environments.
In many environments, position can be accurately estimated by using positioning methods based on the Global Positioning System (GPS). However, GPS-based positioning often provides unsatisfactory performance in certain urban and/or indoor environments. Complementary and/or alternative network-based and network-assisted positioning methods are known. For example, the wireless network provides location assistance information for assisting positioning based on Global Navigation Satellite System, GNSS, signals referred to as Assisted GNSS or A-GNSS. Such assistance data allows wireless devices to use GPS to determine their location in operating environments where GPS-based positioning would not otherwise work or at least would not yield satisfactory results.
Additionally or alternatively, networks may perform uplink, UL, and/or downlink, DL, based positioning. These methods of positioning generally rely on the known, fixed positions of radio nodes within the network, and use cell identifiers and signal measurements for determining the positions of wireless devices operating within the network. Example measurements include Observed Time Difference of Arrival, OTDOA, measurements and such network implement positioning techniques based on such measurements.
Positioning-related measurements may be performed on DL signal and/or on UL signals. In the DL case, initial measurements are taken with respect to one or more DL signals received at a given mobile device, and the mobile device carries out positioning calculations based on the initial measurements, or provides measurement information to the network, for ultimate determination of position. In the UL case, the network makes UL signal measurements and determines the position of the involved mobile device based on those measurements. Certain challenges are encountered in the UL case, however.
For example, UL-based positioning as conventionally practiced has a heavy dependency on the involved network nodes and that limits its application. Further, according to current network standards, such as those promulgated by the Third Generation Partnership Project, 3GPP, for Long Term Evolution, LTE, networks, UL-based positioning is not available via user-plane signaling. Thus, current implementations of UL-based positioning in such networks rely on control-plane signaling. Still further, some of the parameters currently required for UL-based positioning are not efficiently signaled between the relevant nodes within the network, or simply are not available from such nodes in a timely fashion.